Clinical studies have revealed that the concentration of certain compounds in the skin of a subject may be used to assess the risk of development of specific medical conditions in that subject. Early detection of these types of risks in a patient permits measures to be taken that may slow or even prevent the onset of these conditions. As an example, it has been determined that elevated concentrations of cholesterol in the skin of an individual is an indication of a risk for cardiovascular disease. Therefore, the development of simple, non-invasive methods for determining the concentration of skin compounds is of importance.
In U.S. Pat. No. 6,365,363, Parfenov et al. describe a method of indirectly measuring the concentration of cholesterol in the skin of a subject by enzymatically oxidizing the cholesterol in a section of the subject's skin and then quantitating the amount of the hydrogen peroxide by-product stoichiometrically formed in this reaction using a second enzymatic reaction. As a complex series of enzymatic reactions are used in this method to indirectly determine the concentration of cholesterol, the method is both costly and prone to error. In addition, the development of a result using this method is time consuming.
In U.S. Pat. Nos. 6,236,047 and 6,040,578, Malin et al. describe a method for determining the concentration of a blood compound using light in the near-infrared range by analysing diffusively reflecting radiation emerging from the irradiated sample. However, there is no teaching in these patents as to the determination of concentrations of constituents in the skin of a subject.
Hall et al. also describe in U.S. Pat. No. 5,361,758 a non-invasive technique for directly measuring the concentration of constituents of blood using light in the near-infrared range. No specific methods for the determination of compounds within skin are provided.
It is an object of the invention to overcome disadvantages of the prior art.
The above object is met by the combinations of features of the main claims, the sub-claims disclose further advantageous embodiments of the invention.